title: Selective coupling of type 6 adenylyl cyclase with type 2 IP3 receptors mediates direct sensitization of IP3 receptors by cAMP.
abstract: Interactions between cyclic adenosine monophosphate (cAMP) and Ca(2+) are widespread, and for both intracellular messengers, their spatial organization is important. Parathyroid hormone (PTH) stimulates formation of cAMP and sensitizes inositol 1,4,5-trisphosphate receptors (IP(3)R) to IP(3). We show that PTH communicates with IP(3)R via "cAMP junctions" that allow local delivery of a supramaximal concentration of cAMP to IP(3)R, directly increasing their sensitivity to IP(3). These junctions are robust binary switches that are digitally recruited by increasing concentrations of PTH. Human embryonic kidney cells express several isoforms of adenylyl cyclase (AC) and IP(3)R, but IP(3)R2 and AC6 are specifically associated, and inhibition of AC6 or IP(3)R2 expression by small interfering RNA selectively attenuates potentiation of Ca(2+) signals by PTH. We define two modes of cAMP signaling: binary, where cAMP passes directly from AC6 to IP(3)R2; and analogue, where local gradients of cAMP concentration regulate cAMP effectors more remote from AC. Binary signaling requires localized delivery of cAMP, whereas analogue signaling is more dependent on localized cAMP degradation.
authors.affiliation: Department of Pharmacology, Univesrsity of Cambridge, Cambridge, England, UK.
authors.forename: Stephen C
authors.initials: SC
authors.lastname: Tovey
authors.forename: Skarlatos G
authors.initials: SG
authors.lastname: Dedos
authors.forename: Emily J A
authors.initials: EJ
authors.lastname: Taylor
authors.forename: Jarrod E
authors.initials: JE
authors.lastname: Church
authors.forename: Colin W
authors.initials: CW
authors.lastname: Taylor
mesh_terms: D000067956:Adenylyl Cyclase Inhibitors; D000262:Adenylyl Cyclases / Q000378:metabolism*; D020013:Calcium Signaling / Q000187:drug effects; D002217:Carbachol / Q000494:pharmacology; D002460:Cell Line; D002463:Cell Membrane Permeability / Q000187:drug effects; D005576:Colforsin / Q000494:pharmacology; D000242:Cyclic AMP / Q000494:pharmacology*; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism; D019205:GTP-Binding Protein alpha Subunits, Gs / Q000378:metabolism; D020662:Guanine Nucleotide Exchange Factors / Q000378:metabolism; D006801:Humans; D053496:Inositol 1,4,5-Trisphosphate Receptors / Q000378:metabolism*; D007365:Intercellular Junctions / Q000187:drug effects / Q000378:metabolism; D007545:Isoproterenol / Q000494:pharmacology; D010281:Parathyroid Hormone / Q000494:pharmacology; D010727:Phosphoric Diester Hydrolases / Q000378:metabolism; D011485:Protein Binding / Q000187:drug effects; D020033:Protein Isoforms / Q000378:metabolism
chemical_list: D000067956:Adenylyl Cyclase Inhibitors; D020662:Guanine Nucleotide Exchange Factors; D053496:Inositol 1,4,5-Trisphosphate Receptors; C470125:PTH protein, human; D010281:Parathyroid Hormone; D020033:Protein Isoforms; D005576:Colforsin; D002217:Carbachol; D000242:Cyclic AMP; D017868:Cyclic AMP-Dependent Protein Kinases; D010727:Phosphoric Diester Hydrolases; D019205:GTP-Binding Protein alpha Subunits, Gs; D000262:Adenylyl Cyclases; C121100:adenylyl cyclase 6; D007545:Isoproterenol